A transponder is generally a compact, relatively inexpensive electronic device which includes a memory capable of storing a relatively small amount of data. Transponders having either reprogrammable or one-time programmable memories are known. With a reprogrammable memory, information stored in the memory can be changed and/or updated as often as desired. Additionally, information can be read from the memory as often as desired. A reprogrammable memory is also referred to in the art as a "read/write" type of memory. With a one-time programmable memory, on the other hand, information can be written to the memory only a single time. Thereafter, the stored information can be read from the memory as often as liked, but the information cannot be changed or updated. One-time programmable memories are often referred to in the art as "write once/read many" type of memories.
Transponders may include an internal power source or, alternatively, transponders can be parasitically powered. Internally powered transponders include an internal power supply, such as a battery, for powering transponder operations. The service life of such transponders is limited by the power supply. In contrast, parasitically powered, or passive, transponders do not have an internal power source. Instead, such transponders receive power from an external device such as an interrogation unit. Passive transponders potentially have a very long service life, because the service life of such transponders is not limited by the amount of power stored in an internal power supply.
In a typical transponder operation, an interrogation unit is used to transmit an interrogation signal to the transponder. An antenna incorporated into the transponder receives the interrogation signal. Circuitry processes the interrogation signal and develops a response signal whose content depends upon the transponder's programming and circuitry. After developing the response signal, the transponder then transmits the response signal back to the interrogation unit. Based upon the nature of the response signal, appropriate follow-up action can be taken. If the transponder is of the passive type, circuitry coupled to the antenna also converts the interrogation signal into an accumulated voltage. Such voltage is used to power transponder operations. Transponders have been widely described in the literature, including U.S. Pat. Nos. 5,150,114; 5,041,826; 4,463,706; 4,463,353; 4,459,590; 4,364,043; 4,325,146; 4,129,855; and 4,114,151.
A unique sequence of data bits corresponding to a specific identification code can be easily stored in the memory of a transponder. As a result of this characteristic, the electronic identification tags incorporating transponders have been used as a way to assign unique identification codes to various items or entities. For example, U.S. Pat. No. 5,028,918 describes the use of electronic identity tags for animal identification purposes, herd management, security systems, inventory control, process control, and monitoring the functions of an animal, such as feeding, body temperature and milk production. See also U.S. Pat. Nos. 5,499,626; 5,511,553; and 4,857,893.
It is often desirable when assigning a unique identification code to an object or entity to also create a separate data base record corresponding to the item or entity which contains information concerning the item or entity. To facilitate use of such records, the records may be correlated to the identification code so that the code can be used to access the record easily. Typically, such records are created separately from the step of attaching the identity tag to the object. Such an approach may be acceptable if only a few items are to be tagged, but can become more laborious as the number of items to be tagged increases. Additionally, creating records in a separate step increases the chances of errors occurring when correlating the record to the corresponding identification code. It would be desirable if a unique identification code can be associated with an object or entity while simultaneously creating a separate record of the association.
Transponders incorporating identification codes have been associated with human patients and animals using invasive techniques. For example, U.S. Pat. No. 5,499,626 describes an approach in which a transponder is subcutaneously injected into a human patient or an animal using a transponder injection device. With human patients in particular, it would be more desirable if the use of invasive techniques could be avoided.
Transponders incorporating identification codes have been associated with animals by incorporating a transponder onto a tag and then attaching the tag to the animal in some fashion. For example, U.S. Pat. No. 4,854,328 describes attaching such a tag to a hole punched through an animal's ear. Similarly, U.S. Pat. No. 4,463,706 shows attaching such a tag to a collar worn around an animal's neck. With these kinds of approaches, however, the transponders are associated with a particular tag at the outset. Little flexibility is offered to add an additional transponder to a tag if desired. Further, changing the transponder, if desired due to device failure for example, would require replacement of the entire tag. Further, it may be desirable to attach a transponder to an animal without damaging the animal or, in the case of livestock or other large animals, without requiring the animal to wear a collar.